Table of contents

What is T Beam?

A T beam is called so because it is in the shape of the English alphabet “T”. The main application of T beam is in the construction of various engineering structures.

A T beam has a load bearing structure and can be designed by using a number of materials such as wood, reinforced concrete or metal etc.

The cross section of T beam acts as a flange or we can say it compression member for resisting compressive stresses.

The vertical section that is, web resists the shear stress. Web is present below the compression flange. Also the function of web in T beam is to impart larger separation for the coupled bending forces.

As compared to I beam, the difference is that in I beam there is a bottom flange whereas there is no bottom flange in the case of T beam and hence the T beam will not be able to resist the tensile forces and it is a major drawback of the T beam.

We can overcome the above problem by using the T beam in inverted shape that is,inverted T beam having a bridge deck or floor slab which helps in joining the top of the beams and hence this will improve the efficiency of the T beam. When these floor slab or bridge deck if implemented properly then these acts as the compression flange and the drawback can be minimized to a large extent.

A T beam consists of a narrower stem as compared to the ordinary rectangular beam.

The flexural capacity of the T beam depends on the sign of the moment that is, positive moment or negative moment.

If the moment is positive than the resistance of T beam is larger and this is due to the compression in flange section.

If the moment is negative then it is equivalent to the beam without any flange and strength remains as it is.

The designing of a T beam is based in the location of the moment of as the case of its flexural strength and if the moment is positive then we have three cases which are to be checked before designing one of the neutral axis is within the flange having two neutral axis which are outside the flange or present in the web and 3 doubly reinforced beams.

Design of a T Beam

There are multiple elements which play a key role in designing the T beam.

Following are some of the points which are followed for designing T beam:

First of all we determine the maximum amount of the reinforcement permitted by ACI code.

Then we determine the depth of the block that is, rectangular stress block in concrete by using the equation involving moment strength.

Number and the bar diameter are selected and the minimum clear space in between the bars has to be maintained.

Finally the cross section in addition to the required reinforcement is drawn properly and neatly by an appropriate drawing scale.

RCC T- Beam

RCC – Reinforced Cement Concrete

Concrete if used alone is brittle.

Here,

B is the effective width of the flange

Br is the width of the rib

dr is the thickness of the flange slab

d is the effective depth of T beam

A RCC beam comprises of a rib and a flange in the form of T. Top part of the slab which is acting along the beam and used for resisting the compressive stress is termed as a flange. And the part that lies below the slab and used for resisting the shear stress is termed as rib.

Dimension of T Beam

The flange’s effective width is considered as minimum of c/c distance of the nearby beams and ribs.

The complete thickness of the slab which crosses over the beam is considered as flange thickness.

The width of the rib is on down earth ground. It can range from 1/3 to 2/3 of the general depth of the beam.

The depth of the T beam ranges from 1/10 to 1/20 of the span. It can also be calculated by using the following formula

d = ( M * r ) / ( t * J * br )

where,

r is the proportion of the cost of steel and the cost of the concrete

br is the breadth of the rib.

M is the maximum bending moment.

Advantages of T beam

If the span of the beam is larger than 4 m then the resistance offered by the beam is significantly large as compared to the rectangular beam. Basically we can say that the T beam will reduce the requirement of rebar.

A considerable amount of reinforcement, generally ranging from 9% to 20% , can be saved in contrast to the rectangular beam.

The flange or the web of the T beam contribute against the sagging moment and hence the required depth of the beam can be reduced.

Disadvantages of T Beam

Calculations are a bit complex and hence increases the work of drafting for the draftsmen, headache for structure engineers and bar bending for the foreman.

The requirement of the links on the top flange also increases the work of foreman.

The quantity of steel is saved but the extra bar bending work is increased.